During cardiopulmonary bypass surgery the patient's blood is pumped through an extracorporeal blood circuit conventionally comprising a venous drainage line, a venous reservoir, a blood pump, an oxygenator, and an arterial filter. Blood is drained from the patient through the venous drainage line into the venous reservoir. The blood pump draws blood from the reservoir and supplies the blood to the patient via the oxygenator and the arterial filter. The venous reservoir as well as the arterial filter removes air bubbles from the blood, which may otherwise pose a serious risk to the patient's life if returned to the patient in the arterial blood flow.
To avoid the venous reservoir an extracorporeal blood circuit may comprise, as described in U.S. Pat. No. 6,524,267, an arterial filter especially adapted to comprise an air chamber, an purge port having an increased size for allowing a vacuum to actively purge air from the air chamber, a check valve being incorporated into the purge port to prevent air or blood from a cardiotomy reservoir from being drawn into the arterial filter by the negative pressure in the arterial filter, when the purging vacuum is not active, and an air sensor being connected to activate the purge vacuum when, and only when, air is present in the air chamber of the arterial filter.
Arterial filters are known in the art, for example from U.S. Pat. No. 5,632,894, U.S. Pat. No. 4,676,771, U.S. Pat. No. 4,572,724, and U.S. Pat. No. 4,411,783. However, conventional air filters cannot be used in the above second extracorporeal blood circuit although it would be cost saving if conventional components can be used in setting up extracorporeal blood circuit.